Straining apparatuses



United States Patent T 3,232,436 STRAINING APPARATUSES Nils Gunnar Holger Nilsson, Segerminnesvagen 7, Stuvsta, Sweden Filed Feb. 5, 1962, Ser. No. 171,206 Claims priority, application Sweden, Feb. 9, 1961, 1,331/61 4 Claims. (Cl. 210298) This invention relates to straining apparatuses for liquid suspensions, particularly fibrous suspensions such as wood pulp and the like. Within e.g. the pulp and paper industry such apparatuses are also sometimes called Sorters.

More in detail the invention is concerned with that kind of straining apparatuses as defined in which straining of the suspension takes place through stationary, perforated screens of circular cross section under agitation of the suspension by means of rotary stirrers having winglike portions passing rather close to the one side of the screens to thereby cause pulsations in the suspension for promoting the straining.

It is well known that coarse and hard impurities, such as metal pieces, stones and the like, are frequently contained in the suspensions to be treated in the apparatuses and in the hitherto known types of those straining apparatuses there is a considerable risk that such hard pieces get stuck between the stirrer wings and the screens so that the screens tear and other damages occur. The interruptions in the operation of the apparatus which is then necessary for repairs are, of course, very undesirable.

It is the main object of this invention to provide an improved straining apparatus in which the risk for damages of this kind is substantially eliminated so that the apparatus is capable of operating continuously for very long periods without needing any repairs but only ordinary attention, and now and then, removal of collected foreign matters.

Another object of the invention is to provide an improved straining apparatus of the kind referred to which may be built up from a limited number of prefabricated or standard units and which can then be adapted to meet practically any demand as regards capacity and output by suitable multiplication of some of these units without therefore requiring increased floor space or increasing rapidly in high. This is particularly valuable in installations where space is scarce and where it is desirable to increase the capacity of an apparatus which is already installed. Assembling apparatuses of various sizes from a few standard units also keeps the manufacturers costs at a minimum.

These and other objects as well as the features of the invention will more clearly appear from the following detailed description of a preferred embodiment thereof which has been illustrated on the accompanying drawing wherein FIG. 1 is a sectional elevation of a straining apparatus and FIG. 2 is a horizontal section taken along line 2-2 in FIG. 1.

The straining apparatus shown consists of a lower base structure, which is provided with a central hub portion 1 supporting in suitable bearings a vertical stirrer shaft 2, the lower end of which carries a pulley or wheel 3 which is intended to be driven through a suitable transmission by a motor (not shown). If desired, the base structure 1 may alternatively enclose an electric driving motor, the output shaft of which could then be directly extended upwards through hub 1 to constitute the stirrer shaft 2.

The base structure 1 has along its upper outer edge an annular flange 1", which carries a bottom section 4 of the straining apparatus. This bottom section 4 has the 3,232,436 Patented Feb. I, 1966 shape of an inverted bowl with a stuffing-box 5 for the passage of the stirrer shaft 2 in its centre and an upwardly directed confining wall portion along its circumference. This latter wall portion forms the lower part of the cylindrical outer casing of the apparatus and is provided with at least one outlet 6.

The base structure 1 as well as the bottom section 4 are used with all sizes of the apparatus shown, and on the rim of the bottom section 4 there are mounted a number of intermediate sections 7, all of which are identical and substantially cylindrical in shape. In the drawing there are piled two such sections 7 on top of each other to form the outer casing of the apparatus, but it will be readily understood that the number of such sections may be less or greater dependent on the desired size and capacity of the apparatus to be built. As will appear hereinafter the intermediate sections 7 may also be entirely omitted when a minimum size of the apparatus is desirable. Each intermediate section 7 is provided with upper outlets 6', 6" respectively corresponding to the said outlet 6 in the bottom section 4 and intended for the discharge of the residue, and also with outlets 8, 8', respectively, which are placed somewhat lower than the outlets 6', 6" and intended for the discharge of the liquid suspended material that has passed through the screen of the related section of the apparatus. In addition to the arbitrary number of intermediate sections 7 the outer casing of the apparatus comprises a top section 9 which has also the shape of an inverted bowl and which is provided with a detachable top lid 10 giving access to the interior of the apparatus for inspection and like purposes as well as with a tangentially directed inlet 11 for the suspension to be treated. The top section 9, which, if desired, may be placed directly on the bottom section 4 without intermediate sections 7 in case a minimum size apparatus is to be assembled has near its lower edge an outlet 8" corresponding to the outlets 8, 8' of the inter mediate sections 7.

Inside each of the various casing sections 7 and 9 respectively is a strainer chamber insert generally designated by numeral 12 and consisting of a hollow frustoconical, perforated screen 13, the lower, wider end edge of which is secured to a ring 14 interposed with a sealing fit between adjacent ones of the piled botom and casing sectionsas the case may beto keep the inserts in place. The upper, narrower inlet end edge of each screen 13 is in turn secured to a ring 15, which forms a reinforcing support and attachment for the upper edge of a likewise frusto-conical but unperforated cap 16 extending downwards over the outside of the screen 13 at some distance from the latter. The lower, outer preferably also reinforced rim of each cap 16 is adapted to seal with a snug fit against the inside of the related outer casing section 7 or 9 respectively. Thus, each screen 13 will have its lower edge located directly above its related outlet 6, 6 or 6" and directly below its related outlet 8, 8 or 8", while the lower edge of each cap 16 will seal against the outer casing directly above each of said related outlets 8, 8 and 8" respectively and thus be located directly below the next higher outlet 6 and 6" respectively, when the apparatus includes one or more intermediate sections 7, and will in all cases form a conical bottom member in the top casing section 9. The annular space left between each screen 13 and its related cap 16 of each inset 12 will thus be in free communication with one of the outlets 8, 8 or 8".

The shaft 2 extends centrally through the apparatus and carries a number of stirrers in the form of groups of spoke-like arms 17 spaced vertically from each other by spacing sleeves 18. Each arm 17 is substantially T- shaped and carries at its outer ends in an adjustable manner well known per so at wing-like impeller member 19,

which by rotation of the shaft 2 is brought to pass rather close by the inside of the related screen 13. Through a suitable design of the cross-section of the impeller wings 19, such as disclosed in Knight, Patent No. 2,230,647, which design per se forms no part of this invention, the movements of the latter will .result in pulsations in the suspension contained in the apparatus, i.e. pressure variations in the radial direction of each screen, which have proved to considerably improve the straining operation. Obviously each screen 13 requires its own series of arms 17 and impeller wings 19 as shown. Consequently, the number of stirrers in the apparatus and thus also the length of the shaft 2 must be varied in accordance with the size of the apparatus, i.e. with the number of intermediate sections 7 used. In its simplest form and its minimum size the apparatus consists only of the bottom section 4, the top section 9, single insert 12 and a single stirrer 17, 19. The section system makes it possible to build up a straining apparatus of any desired size at the lowest possible cost.

Obviously there is practically no risk that impurities, which could possibly followthe suspension through the inlet 11' and are not prevented from reaching the interior of the apparatus already by the centrifugal action in the top section 9, will get stuck between the moving impeller wings 19 and the screens 13 and cause any serious damage. Instead, they will discharge quickly through the outlets 6, 6' and 6" together with the residue thanks to the construction and location of the screens.

In thecase as shown where the apparatus has several outlets for the accepted material which has already passed the screens and the residue respectively, the outlets 6,- 6' and 6" may as well as the outlets 8, 8' and 8", of course, be interconnected to discharge their respective materials into each a common collector conduit.

As will be seen from the drawing a very compact design of the-apparatus -is obtained by the fact that each upper screen 13 may have its lower edge sealing against the housing at a level below the upper edge of the screen next below. This is possible because the caps 16 are also tapering upwardly.

The cap 16 of the upper insert 12 in the housing forms an annular bottom within the top section 9 of the apparatus, over the raised inner edge of which the suspension is forced to flow in radially inwards direction to enter from the inlet 11 to the different screens 13. In addition to the centrifugal action produced in the suspension as a result of the tangentially opening inlet 11 this overflow action will cause any larger impurities to collect already in the upper compartment of the apparatus.

, I claim:

1. A straining apparatus for liquid suspensions comprising a housing including an upwardly convex bottom portion, a top portion and a substantially cylindrical wall portion therebetween;

means defining an inlet for the liquid suspension to be strained and which opens into said top portion of the housing;

at least one insert in said housing, each insert including a frusto-conical, open-ended perforated screening member arranged with its relatively large diameter end lowermost and in sealing engagement with said cylindrical wall portion of the housing, and a Efrusto-conical, open-ended cap member also arranged with its relatively large diameter end lowermost, said cap member having its upper end edge in sealing engagement with the upper end edge of the related screening member and flaring radially outward from the latter, said lowermost end of said cap member being in sealing engagement with said cylindrical wall portion of the housing and being spaced vertically upward from the lowermost end of the related screening member;

means defining upper and lower outlets for each insert in said housing, said upper outlet opening from said housing at a level intermediate said lowermost ends of the related screening member and cap member, respectively, and said lower outlet opening from said housing at a level immediately below said lowermost end of the related screening member;

a vertical rotary impeller shaft extending centrally in said housing;

a plurality of radial arms extending from said shaft for each insert in said housing; and

an elongated impeller member on the outer end of each of said arms extending parallel to the generatrix of the related frusto-conical screening member and being closely adjacent to the inner surface of the latter so that, when said shaft is rotated and a liquid suspension is introduced at said inlet, the impellers produce pulsations inthesuspension in directions toward and away from the related screen member.

2. A straining apparatus as in claim 1; wherein said inlet opens tangentially into said housing at a level below said upper end edge of said cap member so that the suspension introduced through said inlet overflows radially inward over said upper end edge ofthe cap member after being subjected to centrifugal action.

3. A straining apparatus as in claim 1; wherein a plurality of said inserts are disposed one above the other in said housing; and wherein each insert which is disposed above another of said inserts has the lowermost end of its screening member in sealing engagement with said cylindrical wall portion at a level substantially below that of the upper end edges of the screening and cap members of the next lower insert, thereby to minimize the over-all height of said housing, and each insert which is disposed below another of said inserts has the lowermost end of its cap member in sealing engagement with said cylindrical wall portion at a level immediately below that of said lower outlet for the next higher insert.

4. A straining apparatus as in claim 3; wherein said housing has separable lower and upper sections forming said bottom and top portions, respectively, and parts of said cylindrical wall portion; and wherein said housing further has an intermediate section interposed between said lower and upper sections for each insert more than one disposed in said housing and also forming part of said cylindrical wall port-ion; and

wherein said part of the cylindrical wall portion formed by said lower section has said lower outlet for the lowermost of said inserts in the housing, said part of the cylindrical wall portion formed by said upper section has said upper outlet for the uppermost of said inserts, and said intermediate section has the upper outlet for one of said inserts and the lower outlet for the next higher insert.

References Cited by the Examiner UNITED STATES PATENTS 2,975,899 3/1961 Cannon.

FOREIGN PATENTS 1,257,923 2/1961 France.

619,419 2/1961 Germany.

REUBEN FRIEDMAN, Primary Examiner.

FRANK W. LUTTER, Examiner. 

1. A STRAINING APPARATUS FOR LIQUID SUPENSIONS COMPRISING A HOUSING INCLUDING AN UPWARDLY CONVEX BOTTOM PORTION, A TOP PORTION AND A SUBSTANTIALLY CYLINDRICAL WALL PORTION THEREBETWEEN; MEANS DEFINING AN INLET FOR THE LIQUID SUSPENSION TO BE STRAINED AND WHICH OPENS INTO SAID TOP PORTION OF THE HOUSING; AT LEAST ONE INSERT IN SAID HOUSING, EACH INSERT INCLUDING A FRUSTO-CONICAL, OPEN-ENDED PERFORATED SCREENING MEMBER ARRANGED WITH ITS RELATIVELY LARGE DIAMETER END LOWERMOST AND IN SEALING ENGAGEMENT WITH SAID CYLINDRICAL WALL PORTION OF THE HOUSING, AND A FRUSTO-CONICAL, OPEN-ENDED CAP MEMBER ALSO ARRANGED WITH ITS RELATIVELY LARGE DIAMETER END LOWERMOST, SAID CAP MEMBER HAVING ITS UPPER END EDGE IN SEALING ENGAGEMENT WITH THE UPPER END EDGE OF THE RELATED SCREENING MEMBER AND FLARING RADIALLY OUTWARD FROM THE LATTER, SAID LOWERMOST END OF SAID CAP MEMBER BEING IN SEALING ENGAGEMENT WITH SAID CYLINDRICAL WALL PORTION OF THE HOUSING AND BEING SPACED VERTICALLY UPWARD FROM THE LOWERMOST END OF THE RELATED SCREENING MEMBER; MEANS DEFINING UPPER AND LOWER OUTLETS FOR EACH INSERT IN SAID HOUSING, SAID UPPER OUTLET OPENING FROM SAID HOUSING AT A LEVEL INTERMEDIATE SAID LOWERMOST ENDS OF THE RELATED SCREENING MEMBER AND CAP MEMBER, RESPECTIVELY, AND SAID LOWER OUTLET OPENING FROM SAID HOUSING AT A LEVEL IMMEDIATELY BELOW SAID LOWERMOST END OF THE RELATED SCREENING MEMBER; A VERTICAL ROTARY IMPELLER SHAFT EXTENDING CENTRALLY IN SAID HOUSING; A PLURALITY OF RADIAL ARMS EXTENDING FROM SAID SHAFT FOR EACH INSERT IN SAID HOUSING; AND AN ELONGATED IMPELLER MEMBER ON THE OUTER END OF EACH OF SAID ARMS EXTENDING PARALLEL TO THE GENERATRIX OF THE RELATED FRUSTO-CONICAL SCREENING MEMBER AND BEING CLOSELY ADJACENT TO THE INNER SURFACE OF THE LATTER SO THAT, WHEN SAID SHAFT IS ROTATED AND A LIQUID SUSPENSION IS INTRODUCED AT SAID INLET, THE IMPELLERS PRODUCE PULSATIONS IN THE SUSPENSION IN DIRECTIONS TOWARD AND AWAY FROM THE RELATED SCREEN MEMBER. 